This invention relates to a cylinder head cooling structure for a multi-valve engine and more particularly to an improved cooling arrangement for an overhead valve internal combustion engine having multiple valves.
As is well known, overhead valve internal combustion engines have a number of advantages from combustion and induction efficiency standpoints. However, the use of overhead valves greatly complicates the configuration and formation of the cylinder head. That is, it is necessary to form not only the intake and exhaust passages in the cylinder head as well as the combustion chamber and spark plug receiving recess or recesses but also to provide adequate cooling around at least the combustion chamber and the exhaust passages. In addition, it is desirable to provide cooling around the intake passage so as to improve volumetric efficiency.
It is also well known that the performance of the engine can be improved by using multiple and smaller size valves than single large diameter valves and passages. However, as multiple passages are employed, then the problems aforenoted become particularly acute.
These problems and those attendant with conventional cylinder head cooling arrangements may be best understood by reference to FIGS. 1 through 5. FIG. 1 is a partial cross-sectional view taken through a portion of a single cylinder of a conventional engine construction while FIG. 2 is a lower plan view of the cylinder head and FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2 and also along substantially the same plane as that of FIG. 1. FIG. 4 is a further enlarged view of a portion of the cylinder head as shown in FIG. 3 and FIG. 5 is a cross-sectional view taken along the line 5--5 of FIG. 4.
Referring first to FIG. 1, an engine is identified generally by the reference numeral 11 and is illustrated partially and in cross section taken through a single of the cylinders. It is believed that those skilled in the art will understand well how the prior art construction is employed to various types of multiple cylinder engines and, in the same sense, how the invention can be practiced with multiple cylinder engines of any configuration. FIG. 1 may be considered to be a typical view for both the prior art construction and the embodiment of the invention which will be specifically described later.
The engine 11 includes a cylinder block 12 which defines a cylinder bore 13 in which a piston 14 is supported for reciprocation. The piston 14 is connected by means of a connecting rod 15 to a crankshaft in a well known manner. A cylinder head assembly, indicated generally by the reference numeral 16 is affixed to the cylinder block 12 in a well known manner including by means of head bolts 17 which appear in certain of the figures. This cylinder head assembly 16 has a lower surface 18 that engages a cylinder head gasket 19 and closes the cylinder bore 13. A combustion chamber recess 21 is formed in alignment with the cylinder bore 13 and is surrounded by the gasket 19 and lower surface 18 for compression sealing.
A pair of intake passages 22 are formed in the cylinder head assembly 16 on one side thereof and extend from a sealing surface 23 on the outer periphery of the cylinder head 16 and is adapted to be engaged by a suitable induction system including an intake manifold and charge formers (not shown). These intake passages 22 terminate in valve seats formed in the cylinder head recess 21 and intake valves 24 are slidably supported in the cylinder head assembly 16 for controlling the communication of the intake passages 22 with the combustion chamber. These intake valves 24 are operated in a known manner as by an overhead cam assembly 25 which may have any conventional type of construction.
A pair of siamesed exhaust passages 26 extend through the opposite side of the cylinder head and terminate in a surface 27 of the cylinder head 16 to which an exhaust manifold (not shown) is affixed. These exhaust passages 26 extend from exhaust valve seats which are opened and closed by exhaust valve 28 slidably supported in the exhaust side of the cylinder head 16 in a well known manner.
The cylinder block 12 is provided with a cooling jacket 31 through which coolant is circulated in a manner well known in the art. In addition, the cylinder head 16 is provided with a cooling jacket, indicated generally by the reference numeral 32. This cooling jacket 32 extends in proximity to the combustion chamber recess 21 and around at least in part the intake passages 22 and the exhaust passages 26 for providing cooling. In the illustrated construction, coolant is delivered to the cylinder head cooling jacket 32 on the intake side of the engine from the cylinder block cooling jacket 31 through delivery ports 33 which extend through the lower face of the cylinder head surface 18 and which communicate with corresponding openings formed in the upper surface of the cylinder block 12. This coolant then flows across the cylinder head to the exhaust side and cools the exhaust passages 26. This coolant is then discharged down back into the cylinder block cooling jacket 31 through a pair of large discharge ports 34 which are positioned beneath the exhaust passages 26.
The cooling jacket 32 of the cylinder head 16 is formed by a sand core, as is well known in this art. The openings 34 and 33 are provided for the primary purpose of permitting the sand to be removed from the cylinder head casting 16 at the completion of the casting process. However, these openings also serve the purpose of providing water flow passages, as aforenoted.
There is further provided a flow passage 35 (FIGS. 3 and 5) which extends in part through a dividing wall 36 that separates the non-siamese portion of the exhaust passages 36 from each other. This passage 35 communicates with a further discharge port 37 formed in the lower cylinder head surface 18. Coolant flows to the passage 35 from the area around spark plugwalls 38 through passages 39.
As a result of this construction, the water flow through the cylinder head cooling jacket 32 is as shown by the arrows in FIGS. 3 and 5. However, it should be noted that the passageway 35 and discharge port 37 are relatively small and a stagnant water area will be formed around the area between the exhaust passages 26. This can give rise to hot spots which will interfere with the effective cooling of the engine.
It is, therefore, a principal object of this invention to provide an improved engine cooling arrangement for the cylinder head of a multiple valve internal combustion engine.
It is a further object of this invention to provide an improved cylinder head cooling system for an engine having multiple intake and/or exhaust passages wherein it will be ensured that there are no stagnant areas in the flow path and that adequate cooling of all parts of the cylinder head will be provided.